The broad program project goal is to identify sensitive toxic endpoints and sensitive population for chlorinated hydrocarbon (CHC) toxicity. This subproject focuses on the role of bioaccumulating organochlorine pesticides on alligators and largemouth bass, top predator species in which reproductive failure associated with exposure to these substances has been documented in aquatic ecosystems in Florida. Results to date indicate that reproductive failure in these species results to a large extent from decreased embryonic and neonatal viability, and that these effects Are closely associated with wetlands restoration of former agricultural areas. The overall objective of this project is to establish definitely the causes of reproductive failure among alligators and largemouth bass in contaminated sites and to establish causal links between specific adverse effects and exposure to particular CHCs or mixtures thereof. The proposed studies will be primarily field epidemiologic studies with complementary experimental treatment experiments focusing on effects of several persistent CHC pesticides that are characteristic of agricultural reclamation sites, including toxaphene, dieldrin, chlordane, methoxychlor and non-achlor, all of which are on the CERCLA Priority List of Hazardous Substances. Effects of parental and Environmental exposure of alligators and largemouth bass to CHCs in central Florida lakes, including Lake Apopka, will be studied using molecular biologic, histologic, endocrinologic, toxicologic, and other analytical techniques to evaluate embryo development, egg composition, and neonatal health and endocrine function. Specific aim 1 is to determine the relative contributions of fertilization failure, losses during embryonic development, and decreased reproductive success. This aim will be addressed by field epidemiologic studies in alligators and bass. Specific aim 2 is to determine the direct and multi-generational effects on reproductive success, endocrine function and sexual differentiation in largemouth bass, which will be addressed by paired field mesocosm and laboratory treatment studies. Specific aim 3 is to definitely establish the causal role and the life stage(s) affected for selected CHCs in alligators, using controlled experimental field studies.